Yes, IQ can change over time, though less dramatically than many products promise. The best evidence shows that each extra year of education raises IQ by roughly 1 to 5 points. Retaking the same kind of test raises scores through practice, without a matching rise in underlying ability. Brain-training games make you better at the games but show little effect on general intelligence. Scores can shift noticeably in childhood and adolescence, and from adulthood on your rank among people your age tends to be fairly stable, even as raw abilities like processing speed decline with age.
Can IQ change, or is it fixed
It helps to separate two things. Your raw ability, meaning how many problems you can solve and how quickly, changes enormously across life: it rises steeply through childhood, peaks for most abilities in early adulthood, and declines in some areas later on. Your IQ compares that raw ability with people your own age, so it changes only when you move up or down relative to them. (Our article on average IQ by age explains why the average is always 100.)
Rank is surprisingly stable. In Scotland, people who took the same test at age 11 in 1932 and again at about age 77 showed a correlation of 0.63 between the two scores, about 0.73 after correcting for who was available for retesting (Deary et al., 2000). That is high for a gap of 66 years. It also means many people moved: a correlation that size is compatible with plenty of individuals shifting by 10 points or more relative to peers.
Part of any change from one test to the next is simply measurement error. Even well-built professional tests have a margin of a few points, so a difference of 3 to 5 points between two sittings may mean nothing. For more on that, see how accurate IQ tests are.
How IQ changes in childhood and the teenage years
Scores are least stable early in life. A preschooler's score predicts adult IQ only loosely, and stability rises through the school years.
Adolescence still allows real movement. Ramsden and colleagues tested 33 adolescents at ages 12 to 16 and again three to four years later. Some participants' verbal or nonverbal IQ rose or fell by 15 points or more, and those changes matched changes in gray matter in brain regions linked to speech and to hand movements (Ramsden et al., 2011). The study was small, so the exact sizes should be read cautiously, but it shows that a teenager's IQ can change substantially, and not just because of test error.
Intensive early-childhood programs often produce IQ gains that are visible while the program runs and then shrink in the following years, a pattern researchers call fade-out. Their benefits for schooling and later life outcomes are a separate question from their effect on IQ scores.
Can you increase your IQ
Some things reliably raise measured IQ, some raise only test scores, and some do very little. The table summarizes the evidence; details follow.
| Factor | Effect on measured IQ | Strength of evidence |
|---|---|---|
| Extra years of education | Roughly 1 to 5 points per year | Strong: meta-analysis of quasi-experimental studies |
| Moving to a more favorable home environment (adoption) | Gains of several points on average | Moderate to strong |
| Retaking the same or a similar test | Scores rise, often by several points, without matching gains in ability | Strong |
| Commercial brain-training games | Improvement on the trained games; little or no transfer to general ability | Strong evidence of weak transfer |
| Working memory training | Short-term gains on similar tasks; no convincing lasting gain in reasoning | Moderate |
| Learning chess or a musical instrument | Little effect on general ability in well-controlled studies | Moderate |
| Sleep, illness, stress on test day | Can lower a single score temporarily | Consistent, but effects vary |
Education: the clearest effect
The strongest evidence that IQ can be raised comes from schooling. Ritchie and Tucker-Drob (2018) pooled studies of more than 600,000 people that used three designs to get past the obvious problem that brighter children tend to stay in school longer:
- studies that measured IQ before and after additional schooling, controlling for earlier scores;
- studies of policy changes that raised the minimum school-leaving age, which kept whole cohorts in school longer regardless of ability;
- studies comparing children born just before and just after a school-entry cutoff date, who are nearly the same age but have had different amounts of school.
All three designs pointed the same way: each additional year of education raised IQ by roughly 1 to 5 points, with effects that appeared to persist into later life. That is a meaningful, causal effect, and it is consistent with how much reasoning and vocabulary schooling exercises. It does not mean a sixth year of college adds the same as a sixth year of elementary school, and the meta-analysis could not say which parts of schooling matter most. For more, see IQ and education.
Home environment
Adoption studies give another window. In a large Swedish study comparing brothers where one was raised by his biological parents and the other was adopted into a home with more educated parents, the adopted-away brother scored about 4 points higher on average at military conscription (Kendler et al., 2015). Health and environment also matter at the population level, from nutrition to avoiding lead exposure, which is part of the debate covered in nature vs. nurture in intelligence.
Brain training and working memory apps
Brain-training programs reliably make people better at the trained tasks. The problem is transfer. A meta-analysis of working memory training found short-lived improvements on closely related memory tasks and no convincing evidence of lasting gains on nonverbal reasoning, verbal ability or reading (Melby-Lervåg & Hulme, 2013). A large review commissioned for Psychological Science in the Public Interest examined the studies cited by brain-training companies and reached a similar conclusion: extensive evidence that training improves trained tasks, less for closely related tasks, and little for distantly related tasks or everyday cognitive performance (Simons et al., 2016).
Some meta-analyses of specific programs, such as n-back training, report small gains in reasoning. Critics point out that these tend to shrink in studies with active control groups, in which the comparison group also does an engaging task. The mainstream view is that any far-transfer effect is small at best.
Hobbies, lifelong learning and staying mentally active
Chess, music lessons and puzzles are worthwhile for their own sake, but studies with proper control groups have generally found little transfer to general ability (Sala & Gobet, 2017). Observational studies do find that mentally active adults tend to keep their abilities somewhat better as they age, but cause and effect are tangled: people with higher ability are more likely to choose demanding hobbies and jobs in the first place. Learning a new skill makes you better at that skill, which is usually the best reason to do it.
Practice effects: why retest scores rise
If you take an IQ test, or one similar to it, a second time, you will usually score higher. You know the formats, you are calmer, and you may remember strategies or even specific items. A meta-analysis of retesting in personnel selection found gains on cognitive ability tests of roughly a quarter of a standard deviation, about 4 IQ points, and larger gains with coaching (Hausknecht et al., 2007).
That rise is real on paper but it is mostly not a rise in intelligence. It is why clinicians avoid repeating the same test within a short period and why norms assume a first attempt. It is also the honest limit of advice on how to prepare for an IQ test: familiarity helps you show your ability, not grow it. The same applies to online tests, including ours. If you take the free test twice, expect the second result to be somewhat higher for this reason.
Does IQ go down with age
Raw ability does, in some areas. Processing speed, fluid reasoning and some kinds of memory decline gradually through adulthood and faster in later life, while vocabulary and general knowledge hold steady or keep growing into middle age and beyond. Age-normed IQ does not have to drop, because you are compared with people your age; if you decline at the typical rate, your IQ stays about where it was.
Individual differences widen in old age. Cardiovascular health, hearing and vision, sleep, medication, depression and neurological disease all affect test performance. A noticeable drop compared with peers, or changes that disrupt daily life, are worth discussing with a doctor; an IQ test is not a diagnostic tool and this article is not medical advice.
The bottom line
IQ is neither fixed at birth nor freely adjustable. Education has a well-documented effect, environment matters, and teenagers can change markedly. Most products sold as IQ boosters improve performance on their own tasks rather than general ability, and retest gains largely reflect familiarity. If you want your ability to be as high as it can be, the evidence points to ordinary things: more learning, good health, and turning up to a test rested.